1. Field of the Invention
The present invention relates to a semiconductor device production management system, and a semiconductor device production method. More particularly, the invention relates to a production management system for managing operating conditions of wafer carrier cassettes, as well as to a semiconductor device production method involving the use of that production management system.
2. Description of the Background Art
During production of semiconductor devices, wafer carrier cassettes are managed so that the quality and yield of the semiconductor products are improved. A typical method of such management is illustratively disclosed in Japanese Patent Laid-Open No. Hei 6-183524. The disclosed method involves managing the number of times each wafer carrier cassette is used so as to forestall deteriorating conditions associated with the cassette being overused, such as deformation, friction-induced destruction of the cassette in transit, or dust emanating from the cassette itself.
A major factor responsible for deterioration in the quality and yield of semiconductor devices is the spread of contaminants over a semiconductor wafer in addition to the cassette breakdown and dust emanations mentioned above. How contaminants can spread over the semiconductor wafer is outlined below with reference to FIGS. 20 through 23.
FIG. 20 is a perspective view of a wafer carrier cassette 10 which contains wafers 12 and which is used during semiconductor device production. Inside the cassette 10 are a plurality of slits 14 that keep the wafers 12 in place therein.
FIG. 21 is a perspective view of a case 16 accommodating a cassette 10. The case 16 is made up of a body 18 and a base 20 detachable from each other. A handle 22 for manually carrying the case 16 is secured to the body 18.
FIG. 22 is an enlarged view of a tip of the wafer 12 held inside the slit 14. As illustrated, the slit 14 and wafer 12 can bear a substance 24 emanating from semiconductor device production processes. When a wafer 12 bearing the substance 24 following a certain process is inserted into a slit 14, the direct contact between the wafer 12 and the slit 14 leaves the substance 24 stuck inside the slit 14. The wafer 12 is then taken out of the cassette 10 and subjected to a lower end process. Thereafter, the wafer 12 is again inserted into the slit 14. This causes the substance 24 left in the slit 14 to cling back to the wafer 12. The substance 24, required in a certain process, can thus turn into a contaminant in a different process.
FIG. 23 is a schematic view explaining how contaminants can spread over the wafer 12 during semiconductor device production. In the setup of FIG. 23, a product 1 is supposed to be processed by first production equipment 26 alone in the normal course of production. In this example, the product 1 is shown processed by second production equipment 30 by human error after being processed by the first production equipment 26. In such a case, a second substance 32 used inside the second production equipment 30 can be contaminated by a first substance 28 stuck to the wafer 12 in the first production equipment 26.
In FIG. 23, a product 2 is supposed to be processed by the second production equipment 30. If the second substance 32 has come to be contaminated by the first substance 28 as described above, the product 2 is polluted by the first substance 28 while being processed by the second production equipment 30. In this manner, an error in the production flow of a single product can give rise to in-process contamination.
In the example of FIG. 23, a product 3 is supposed to be processed by the first production equipment 26 alone in the normal course of production. In this example, the product 3 is shown processed by the first production equipment 26 before being transferred by human error into a cassette that should be dedicated in use only to a process involving the second substance 32. In such a case, the transferred wafer 12 is contaminated by the second substance 32 that came off the dedicated cassette. In this manner, an error in the movement of a cassette of a single product can trigger in-process contamination.
As outlined above, human error in conventional semiconductor device production processes can often result in contamination of products. What follows is a brief supplementary explanation of how such contamination can affect the characteristics of semiconductor devices.
FIG. 24 is an enlarged view of a gate portion and its surroundings in an MOS transistor. The MOS transistor FIG. 24 has a gate insulating film 36 and a gate electrode 38 formed on a wafer 12. The gate insulating film 36 includes an insulation-deteriorated portion 40, i.e., a portion where a contaminant has deteriorated the quality of the film. Typical contaminants producing the insulation-deteriorated portion 40 are metals. Among the metals, particularly aluminum (Al) and copper (Cu) are liable to trigger high degrees of contamination due to large diffusion coefficients thereof. In FIG. 24, a voltage applied between the gate electrode 38 and the wafer 12 causes a large leak current 44 to flow through the insulation-deteriorated portion 40. Once the insulation-deteriorated portion 40 is formed, the MOS transistor can no longer function with correct electrical characteristics.
It is therefore an object of the present invention to overcome the above and other deficiencies of the prior art and to provide a semiconductor device production management system that effectively prevents the diffusion of contaminants caused by human error.
It is another object of the present invention to provide a semiconductor device production method for producing high-quality semiconductor devices at high yield rates using the inventive production management method.
The above objects of the present invention are achieved by a production management system for managing production of semiconductor devices. The system includes usage rule storing means for storing usage rules on containers for accommodating wafers with regard to individual processes included in a reviewable process flow. The system also includes reviewable process flow checking means for checking whether the reviewable process flow complies with the usage rules.
The above objects of the present invention are achieved by a production management system for managing production of semiconductor devices. The system includes production line process flow storing means for storing a plurality of processes included in a production line process flow for use on a semiconductor device production line. The system also includes container condition storing means for storing usage rules on containers for accommodating wafers with regard to each of the processes included in the production line process flow. The system further includes usage rule supplying means for supplying the usage rules regarding the containers to either pieces of production equipment for executing the processes included in the production line process flow, or to devices installed close to the pieces of production equipment.
The above objects of the present invention are achieved by a semiconductor device production method for producing semiconductor devices by use of a production management method described above.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.